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Cell Biology

5 lectures + background reading (Campbell)

  1. Cell structure (chapter 7)
  2. Cell membranes (chapter 8)
  3. Cell division (chapter 12)
  4. Respiration (chapter 10)
  5. Photosynthesis (chapter 11)

Assessment

MCQ Exam

  • MCQ, 20 questions, 30 minutes
  • 31st October, 16:00
  • 1 week after last lecture

Practical: Mitosis in onion root tips

  • Dr. Owen Osbourne
  • 27th or 28th November

Self study

Cells are everywhere!

  • Basic structural unit(s) of all organism
  • Single-celled to multicellular organisms
  • There are 2 types:
    • Prokaryotic
    • Eukaryotic

Cells are everywhere!

Cells are everywhere!

Cells are everywhere!

Cells are everywhere!

Prokaryotic cells

  • Bacteria and Archaea
  • Chromosomes, plasma membrane, cytoplasm, ribosomes
  • Small (1-5um)
  • DNA in nucleoid (no membrane)
  • Ubiquitous in all ecosystems

Prokaryotic cells

  • Outnumber human cells 10:1
  • ~2kg mass

Eukaryotic cells

  • Animals, plants, fungi, protists
  • Chromosomes, plasma membrane, cytoplasm, ribosomes
  • Large (10-100 um)
  • DNA in nucleus (with membrane)
  • Membrane bound organelles

Simple Eukaryotic cell diagram

  • Membrane
  • Nucleus
  • Cytoplasm
  • Organelles


Animal cell

Plant cell

Microscopy

Nucleus

Nucleus

  • Large!
  • Contains most of the cell’s DNA (genome)
  • DNA has genes that encode proteins
  • Chromosomes + proteins = chromatin
  • Nuclear envelope: Double membrane with pore complex
  • Allows export of messenger RNA (mRNA)

Nucleus

Endoplasmic reticulum (ER)

  • Network of membranes

  • Form tubules and sacs called cisternae

  • The internal part of cisternae are called the ER lumen

  • Separated from cytoplasm and connected to nuclear envelope

  • Rough ER is studded with ribosomes:

    • Synthesise proteins from mRNA
    • Free and bound to endoplasmic reticulum
    • Cells that do lots of protein synthesis have lots of ribosomes

Endoplasmic reticulum (ER)

Rough and Smooth ER

Rough ER

  • Allows protein synthesis isolated from cytoplasm
  • Proteins can exit the ER lumen packaged in membrane vesicles

Smooth ER

  • Important for synthesis of lipids, membrane phospholipids and hormones
  • Detoxification, e.g. drugs and poisons in liver cells
  • Increase in smooth ER improves detoxification (drug/alcohol tolerance)

Golgi apparatus

Golgi apparatus

  • “Warehouse” for sorting and export of ER products
  • Directional, with cis face receiving products from ER
  • Trans face secretes products using vesicles

Lysosomes

Lysosomes

  • Membraneous sac of hydrolytic enzymes
  • Used to digest macromolecules
  • Intracellular digestion
  • Phagocytosis (e.g. within macrophage cells)
  • Autophagy (recycling cell components)

Lysosomes

Phagocytosis

Vacuole

Vacuole

  • Derived from ER
  • Plant and fungal cells often have a large central vacuole
  • Various roles: storage of toxins, pigments, water

Mitochondria

Mitochondria

  • Carry out cellular respiration
  • Convert oxygen + sugar/fats to ATP
  • Number correlates with cell’s metabolic activity
  • Has its own small genome

Mitochondria

Chloroplasts

Chloroplasts

  • Photosynthesis
  • Contain the chlorophyll, as well as enzymes and other molecules that function in photosynthesis
  • Gives plants their green colour
  • Has its own small genome

Cytoskeleton

Endosymbiont theory

  • Ancestor of Eukaryotes engulfed oxygen-using and photosynthetic prokaryotes
  • Became mitochondria and chloroplasts
  • Double membranes
  • Ribosomes
  • Circular genomes (like bacteria)

Lynn Margulis

  • Proposed endosymbiont theory in 1967
  • After rejection from 15 journals!
  • Ignored for a decade
  • Demonstrated experimentally in 1978, widely accepted in 1980s based on genetics
  • Numerous awards and widespread recognition

Cell Biology

5 lectures + background reading (Campbell)

  1. Cell structure (chapter 7)
  2. Cell membranes (chapter 8)
  3. Cell division (chapter 12)
  4. Respiration (chapter 10)
  5. Photosynthesis (chapter 11)

Next time: Cell membranes